Progressive plyometric training improves jumping performance and reduces force-velocity imbalance in collegiate volleyball players

Abstract

Few studies have focused on plyometric interventions lasting over 24 weeks in team-sport athletes, and little research has validated the practical utility of personalized force-velocity assessment. A total of 36 university volleyball athletes (21.35{+/-}1.87 years) were randomly allocated into either a 32-week plyometric training group (PT, n=18) or a low-intensity active control group (CON, n=18); 34 players completed the trial (17 per group). PT completed three weekly training sessions, while CON maintained routine technical practice and general low-intensity conditioning. CMJ height, RSImod, and force-velocity profiles (F, V, peak power, FV imbalance) were evaluated at baseline and at weeks 8, 16, 24, and 32. PT increased CMJ height from 33.1{+/-}4.8 cm to 38.4{+/-}5.2 cm, a net gain of 5.3 cm (p<0.01, d=0.99, 95% CI [0.57, 1.41]); CON showed negligible change (+0.5 cm, p=0.68). The PT group also improved RSImod by 31.6% (d=0.87, 95% CI [0.45, 1.29], p<0.01) and peak power by 18.4% (d=0.76, 95% CI [0.35, 1.17], p=0.004). Meanwhile, FV imbalance dropped markedly by 31.4%, from 28.3% to 19.4% (d=-0.68, 95% CI [-1.09, -0.27], p=0.024). No significant F-V changes occurred in CON. The reduction in FV imbalance correlated moderately with CMJ gain (r= - 0.53, p=0.024), whereas the change in peak power did not (r=0.21, p=0.39). Overall, 32 weeks of periodized plyometric training enhanced jump performance, reactive strength, and power, and reduced the force-velocity (FV) imbalance by approximately 31%. The magnitude of improvements in jump performance (16%) and FV imbalance reduction (31%) observed in this 32-week periodized program fall within a similar range to previously reported effects of individualized F-V training (14% and 40%, respectively). However, direct numerical comparisons are confounded by differences in study design, population, and methodology; head-to-head trials are needed.